An oak tree begins its life cycle with the germination of an acorn which produces a small root, resulting in the growth of a sapling tree. Flowers that have a greenish color appear in the spring on mature trees, producing pollen for fertilization and the growth of new acorns that repeat the life cycle.
Acorns are a large type of seed and the result of a fertilized ovum in an oak tree. Each female flower contains six ovules with eggs, but only one ovule or ovum is fertilized at one time. The time of year that acorns drop from oak trees depends on the species. Some oak trees drop acorns in the fall, while others drop acorns during the early part of the year.
After dropping to the ground, acorns are carried away from the parent tree by weather, water and animals such as squirrels. Over time, the acorn becomes covered with plant debris and soil, creating an ideal environment for growth.
Oak trees grow slowly and live for up to 400 years, according to GardenGuides.com. An oak tree is mature when it begins producing acorns at around 20 years of age. There are over 80 species of oak trees in North America, some of which grow to over 100 feet in height.